Method for allocating resources in wireless communication system and system thereof

ABSTRACT

This invention relates to a method for allocating resources in a wireless communication system and a system thereof. The disclosed method comprises steps for: allowing a user&#39;s terminal to receive information about the wireless transmission resources among semi-permanent transmission resources; performing CRC-calculation by receiving a message about the allocation of the semi-permanent transmission resources based on the received information; verifying the validity of the message by comparing the information about the wireless resources indicated in the received message with the received information about the wireless transmission resources; and receiving data as the transmission resources indicated in the message if there is no error in the verification.

TECHNICAL FIELD

The present invention relates to a wireless communication system andresource allocation method of the wireless communication system and, inparticular, to a wireless communication system and resource allocationmethod thereof for avoiding resource allocation error.

BACKGROUND ART

Universal Mobile Telecommunication Service (UMTS) system is a 3^(rd)Generation asynchronous mobile communication system based on GlobalSystem for Mobile Communication (GSM) and General Packet Radio Services(GPRS) and using Wideband Code division Multiple Access (WCDMA).

The 3^(rd) Generation Partnership Project (3GPP), in charge ofstandardization of UMTS, is now working on Long Term Evolution (LTE) asthe next generation mobile communication system. LTE is a technology forrealizing 100 Mbps high-speed packet based-communication and isscheduled to be commercialized by 2010. In order to meet therequirement, various techniques discussed. Some of these techniques canbe to reduce a number of nodes on the communication channel and toarrange wireless protocols close to wireless channels.

In case of LTE in which communication is performed with the resourcesallocated based on the per-packet scheduling, frequent transmission ofcontrol information such as scheduling request and resource allocationinformation causes traffic overload. In order to solve this problem,Semi-Persistent Scheduling (SPS) is adopted.

In the SPS, the base station notifies a user terminal of the allocatedSPS resource and size of MAC PDU to be transmitted on the SPS resource.Upon receipt of the information on the SPS resource allocation, the userterminal can transmit MAC PDUs on the SPS resource without exchange ofadditional control signals. In order to check the SPS resource allocateditself, the user terminal performs Cyclic Redundancy Checking (CRC). Ifthe CRC fails, the user terminal may misjudge the allocation of SPSresource even though no SPS resource has been allocated. In this case,the user terminal transmits the data continuously on the misjudged SPSresource, resulting in waste of transmission resource allocation. Thereis therefore a need to develop of an efficient resource allocationmethod that is capable of reducing the waste of transmission resource.

DISCLOSURE Technical Problem

In order to solve the problems of the prior arts, the present inventionprovides a wireless communication system and resource allocation methodof the wireless communication that is capable of verifying the validityof the resource allocation message for the semi-persistent transmissionresource by correcting error in CRC result.

Technical Solution

In accordance with an aspect of the present invention, a resourceallocation method of a user terminal includes performing CyclicRedundancy Checking (CRC) operation on a semi-persistent transmissionresource allocation message received; verifying, when the CRC operationsucceeds, validity of the semi-persistent transmission resourceallocation message by comparing transmission resource informationcontained in the semi-persistent transmission resource allocationmessage with a previously received radio transmission resourceinformation; and using, when the validity of the semi-persistenttransmission resource allocation message is verified, the transmissionresource indicated by the semi-persistent transmission resourceallocation message semi-persistently.

Preferably, verifying validity of the semi-persistent transmissionresource allocation message comprises determining whether a MAC PDU sizeindicated in the semi-persistent transmission resource allocationmessage is equal to one of MAC PDU sizes contained in the previouslyreceived radio transmission resource information.

Preferably, the indicated MAC PDU size is a value obtained from a numberof resource blocks, a modulation scheme, a channel coding rate, and anumber of bits per resource block that are acquired from thesemi-persistent transmission resource allocation message.

Preferably, verifying validity of the semi-persistent transmissionresource allocation message comprises determining whether a number ofresource blocks indicated by the semi-persistent transmission resourceallocation message is less than a maximum number of resource blocks ofthe previously received radio transmission resource information.

Preferably, the resource allocation method further includes discarding,when the CRC operation fails, the semi-persistent transmission resourceallocation message.

Preferably, verifying validity of the semi-persistent transmissionresource allocation message includes transmitting an HARQ message to afirst packet transmitted on the transmission resource indicated by thesemi-persistent transmission resource allocation message; and receivingat least one of an HARQ ACK in response to the HARQ message to the firstpacket and a retransmission resource allocation message in response tothe HARQ message.

Preferably, the resource allocation method further includes using, whenat least one of an HARQ ACK in response to the HARQ message andretransmission resource allocation message in response to the HARQmessage is received, the transmission resource indicated by thesemi-persistent transmission resource allocation message.

Preferably, the resource allocation method further includes discarding,when none of an HARQ ACK in response to the HARQ message andretransmission resource allocation message in response to the HARQmessage is received, the semi-persistent transmission resourceallocation message.

In accordance with another aspect of the present invention, a userterminal which is allocated transmission resource by means of asemi-persistent transmission resource allocation message includes areception unit which receives the semi-persistent transmission resourceallocation message, compares, when no error is in CRC operation result,transmission resource information contained in the semi-persistenttransmission resource allocation message with a previously receivedradio transmission resource information to verify validity of thesemi-persistent transmission resource allocation message, and uses, whenthe validity of the semi-persistent transmission resource allocationmessage is verified, the transmission resource indicated by thesemi-persistent transmission resource allocation messagesemi-persistently.

Preferably, the reception unit verifies the validity of thesemi-persistent transmission resource allocation message by comparing aMAC PDU size indicated in the semi-persistent transmission resourceallocation message with MAC PDU sizes contained in the previouslyreceived radio transmission resource information.

Preferably, the reception unit calculates the MAC PDU size based on atleast one of a number of resource blocks, a modulation scheme, a channelcoding rate, and a number of bits per resource block that are acquiredfrom the semi-persistent transmission resource allocation message

Preferably, the reception unit verifies the CRC operation resultdepending on whether a number of resource blocks indicated by thesemi-persistent transmission resource allocation message is less than amaximum number of resource blocks of the previously received radiotransmission resource information.

Preferably, the reception unit discards, if an error is in CRC operationresult, the semi-persistent transmission resource allocation message.

Preferably, the user terminal further includes a radio resource controlunit which receives the radio transmission resource informationincluding at least one of available MAC PDU sizes and maximum number ofresource blocks from a base station.

Preferably, the reception unit verifies the validity of thesemi-persistent transmission resource allocation message, aftertransmitting an HARQ message to a first packet transmitted on thetransmission resource indicated by the semi-persistent transmissionresource allocation message, depending on whether at least one of anHARQ ACK in response to the HARQ message to the first packet and aretransmission resource allocation message in response to the HARQmessage.

Preferably, the reception unit uses, when at least one of an HARQ ACK inresponse to the HARQ message and retransmission resource allocationmessage in response to the HARQ message is received, the transmissionresource indicated by the semi-persistent transmission resourceallocation message.

Preferably, the reception unit discards, when none of an HARQ ACK inresponse to the HARQ message and retransmission resource allocationmessage in response to the HARQ message is received, the semi-persistenttransmission resource allocation message.

Advantageous Effects

As described above, the resource allocation method of the presentinvention is capable of verify the validity of the semi-persistenttransmission resource allocation message even when CRC error occurs,resulting in reduction of waste of semi-persistent transmissionresource. The present invention is advantageous to save radiocommunication resource. Accordingly, it is possible to improve theperformance of the radio communication system.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram illustrating a configuration of thewireless communication system according to an embodiment of the presentinvention;

FIG. 2 is a diagram illustrating a layered structure of protocol stackof the wireless communication system according to an exemplaryembodiment of the present invention;

FIG. 3 is a block diagram illustrating a configuration of the userterminal according to an exemplary embodiment of the present invention;

FIG. 4 is a signaling diagram illustrating the resource allocationmethod of the wireless communication system according to the firstembodiment of the present invention;

FIG. 5 is a diagram illustrating a format of the semi-persistenttransmission resource allocation message according to an embodiment ofthe present invention;

FIG. 6 is a drawing of graphs illustrating packet generation frequencyin accordance with code type and codec rate according to an embodimentof the present invention;

FIG. 7 is a flowchart illustrating a resource allocation methodaccording to the first embodiment of the present invention;

FIG. 8 is a diagram illustrating a transmission resource allocationmethod according to the second embodiment of the present invention; and

FIG. 9 is a flowchart illustrating a transmission resource allocationmethod according to the second embodiment of the present invention.

BEST MODEL Mode for Invention

Exemplary embodiments of the present invention are described withreference to the accompanying drawings in detail. The same referencenumbers are used throughout the drawings to refer to the same or likeparts. Detailed description of well-known functions and structuresincorporated herein may be omitted to avoid obscuring the subject matterof the present invention.

A description is made of the wireless communication system according toan exemplary embodiment of the present invention. FIG. 1 is a schematicdiagram illustrating a configuration of the wireless communicationsystem according to an embodiment of the present invention.

In the wireless communication system according to an embodiment of thepresent invention as shown in FIG. FIG. 1, an Evolved Radio AccessNetworks (hereinafter, called E-RAN) (110 and 112) is implemented as a3-node structure including Evolved Node Bs (ENB) (120, 122, 124, 126,and 128) and Evolved Gateway GPRS Serving Nodes (EGGSN) (130 and 132).Here, GPRS is the abbreviation of General Packet Radio Service.

A User Equipment (UE) (101) accesses the Internet Protocol (IP) network(114) via the E-RAN (110 and 112). The ENB (120, 122, 124, 126, and 128)corresponds to the legacy Node B and allows the connection of the UE100. Unlike the legacy Node B, ENB (120, 122, 124, 126, and 128) is incharge of more complicated functions. The Next generation wirelesscommunication system serves such that the all kinds of user trafficincluding real time services such as Voice over IP (VoIP) aretransmitted on the shared channel. For this reason, the UE (101) needsto be scheduled based on the status information, and the ENB (120, 122,124, 126, and 128) is responsible for the scheduling. An ENB (120, 122,124, 126, or 128) can manage a plurality of cells. In order to securethe maximum data rate of 100 Mbps, the wireless communication systememploys Orthogonal Frequency Division Multiplexing (OFDM) as wirelessaccess technology over the bandwidth of 20 MHz. The wirelesscommunication system can employ the Adaptive Modulation and Coding (AMC)technique for determining the modulation scheme and channel coding ratebased on the channel condition of the UE 101.

The E-RAN (110 and 112) including the ENBs (120, 122, 124, 126, and 128)is called base stations and the UE 101 is called user terminal (100)hereinafter.

Next, a description is made of the layered structure of protocol stackof the wireless communication system according to an embodiment of thepresent invention. FIG. 2 is a diagram illustrating a layered structureof protocol stack of the wireless communication system according to anexemplary embodiment of the present invention.

Referring to FIG. 2, the protocol stack includes a Packet DataConvergence Protocol (PDCP) layer (205, 240), a Radio Link Control (RLC)layer (210, 235), a Medium Access Control (MAC) layer, and a Physical(PHY) layer (220 and 225).

The PDCP layer (205, 240) is responsible for IP headercompression/decompression. The RLC layer (210, 235) is responsible forAutomatic Repeat Request (ARQ) with reconstruction of PDCP PDU (ProtocolData Unit, which is a packet output by a specific protocol layer device)in appropriate size.

The MAC layer (215, 230) is connected with a plurality of RLC layerdevices within the user terminal. The mace layer (215 and 230)multiplexes the RLC PDUs output by the RLC layer devices into MAC PDUand demultiplexes the MAC PDU into RLC PDUs.

The PHY layer (220, 225) performs channel coding and modulation on theupper layer data into OFDM symbols to be transmitted over radio channeland performs demodulation and channel decoding on the OFDM symbolsreceived over the radio channel and transfers the decoded data to theupper layer.

In the wireless communication system according to an embodiment of thepresent invention, all the services are provided in packet-based manner.For example, the voice call service can be provided in packet-switchedmanner rather than circuit-switched manner. Particularly, the VoIPtraffic has a characteristic in that small packet is generatedperiodically. For example, in the VoIP service operating in 12.2 kbpsAMR codec mode, the packet which is 35-byte long in size is generatedevery 20 msec. In order to transmit the VoIP packet with the normalscheduling, the scheduling request information and uplink transmissionresource allocation information have to be transmitted whenever thepacket is generated. For this reason, the base station 200 allocatessemi-persistent resource to the user terminal 100. The messagetransmitted by the base station for allocating semi-persistent resourceis called “semi-persistent transmission resource allocation message”.Meanwhile, the user terminal 100 performs Cyclic Redundancy Check (CRC)for checking whether the received message is the semi-persistenttransmission resource allocation message destined to itself. The CRCoperation error may cause the user terminal to misjudge a transmissionresource allocation message destined to another terminal as thesemi-persistent resource destined itself. Such a message is called“misrecognized erroneous semi-persistent resource transmission resourceallocation message” (hereinafter, called misrecognized erroneousmessage). The present invention is provided to check the misrecognizederroneous message by verifying the CRC operation result.

A description is made of an internal structure of the user terminal 100according to an exemplary embodiment of the present invention. FIG. 3 isa block diagram illustrating a configuration of the user terminalaccording to an exemplary embodiment of the present invention.

Referring to FIG. 3, the user terminal 100 includes a Radio Frequency(RF) unit 110, a reception unit 300, an upper layer device 150, and aradio resource control unit 160. Particularly, the reception unit 300includes a PDCCH processor 120, a transmission resource controller 130,a MAC PDU generator 140, a radio resource controller 150, and upperlayer device 160.

The RF unit 110 is responsible for communicating data over radiochannels. Particularly, the RF unit 110 transmits/receives messages onPhysical Downlink Control Channel (PDCCH). If a message is received overthe PDCCH, the RF unit 110 decodes the message received on the PDCCH andtransfers the decoded message to the PDCCH processor 120.

The PDCCH processor 120 performs masking on message decoded by the RFunit 110 with a Cell Radio Network Temporary Identity (C-RNTI) and CRCoperation. The C-RNTI is an identifier that can be used to identify thesemi-persistent resource allocation message. That is, the PDCCHprocessor 120 performs CRC operation and determines whether the messageis destined to itself. The PDCCH processor 120 sends the transmissionresource allocation message and semi-persistent transmission resourceallocation message identified based on the CRC result, i.e. passed theCRC test, to the transmission resource controller 130.

The transmission resource controller 130 controls the RF unit 110 andthe MAC PDU generator 140 such that the MAC PDU generated in sizeindicated by the resource allocated with the transmission resourceallocation message sent by the PDCCH processor 120.

Particularly, the transmission resource controller 130 according to thefirst embodiment of the present invention is capable of verifying themisrecognized erroneous message received as a result of the erroneousCRC operation.

In more detail, the transmission resource controller 130 receives theinformation on the available MAC PDU size and maximum number of resourceblocks from the radio resource control unit 160. Next, the transmissionresource controller 130 determines whether the semi-persistenttransmission resource allocation message from the PDCCH processor 120 isthe misrecognized erroneous message. If it is determined that thesemi-persistent transmission resource allocation message is not themisrecognized erroneous message, the transmission resource controller130 controls the MAC PDU generator 140 and the RF unit 110 to transmitthe MAC PDU generated in size indicated by the information received onthe semi-persistent transmission resource. If it is determined that thesemi-persistent transmission resource allocation message is themisrecognized erroneous message, the transmission resource controller130 discards the message and ignores the information carried by themessage.

According to the second embodiment of the present invention, thetransmission resource controller 130 receives the semi-persistenttransmission resource allocation message and performs HARQretransmission using the transmission resource indicated by the receivedsemi-persistent transmission resource allocation message. If an HARQresponse message and a retransmission transmission resource allocationmessage is received, the transmission resource controller 130 transmitsand/or receives data on the transmission resource indicated by thereceived semi-persistent transmission resource allocation message.

The MAC PDU generator 140 generates MAC PDUs with the data provided bythe upper layer device 150 and transfers the MAC PDUs to the RF unit110. At this time, the size of MAC PDU determined under the control ofthe transmission resource controller 130.

The upper layer device 150 can be any of Radio Link Control (RLC) deviceand Physical Downlink Control Protocol (PDCP) device. The PDCP device isa device in charge of compression/decompression of IP header, and theRLC device restructures the PDCP PDUs and is responsible for performingARQ operation for reliable data transmission.

The radio resource controller 160 receives the information on theavailable size of MAC PDU and maximum number of resource blocks from thebase station in a call setup process and transfers this information tothe transmission resource controller 130.

Although not depicted in drawings, the user terminal according to anembodiment of the present invention is provided with a storage devicefor storing the received data. The storage device can store the datasuch as the table for saving the size of MAC PDU according to the codecrate, the valid MAC PDU size, and the maximum number of resource blocks.The user terminal also is provided with a decoding device for decodingthe data and/or message related to specific protocol such as the PDCCHprocessor 120. For example, the user terminal can be provided with adevice for decoding the data of a Radio Resource Control (RRC) protocol.The decoding device performs decoding on the data or message of thecorresponding protocol among the data and messages received by the radioreceived connected to the RF unit 110.

A description is made of the radio resource allocation and the datatransmission/reception method using the allocated resource in thewireless communication system according to an embodiment of the presentinvention.

FIG. 4 is a signaling diagram illustrating the resource allocationmethod of the wireless communication system according to the firstembodiment of the present invention, and FIG. 5 is a diagramillustrating a format of the semi-persistent transmission resourceallocation message according to an embodiment of the present invention.

The base station 200 transmits the information on the range or size suchas a number or amount of semi-persistent resources to the user terminal100 at step S401. This information is called “radio transmissionresource information” hereinafter. The radio transmission resourceinformation includes the available MAC PDU size and maximum number ofresource blocks. The available MAC PDU size and maximum number ofresource blocks are transmitted in the call setup process between thebase station 200 and the user terminal 100.

The user terminal 100 receives the semi-persistent transmission resourceallocation message and extracts the transmission resource informationfrom the received semi-persistent transmission resource allocationmessage. The transmission resource information extracted from thesemi-persistent transmission resource allocation message can include theMAC PDU size and number of resource blocks. Accordingly, the userterminal 100 can verify the validity of the semi-persistent transmissionresource allocation message by comparing the MAC PDU size and number ofresource blocks indicated by the semi-persistent transmission resourceallocation message with the previously received available MAC PDU sizeand maximum number of resource block size.

The user terminal 100 stores, at step 403, the information on theavailable MAC PDU size and maximum number of resource blocks that istransmitted by the base station 200. In the call setup process, the basestation 200 transmits the information on the available MAC PDU size andthe maximum number of resource blocks to the user terminal 100 by meansof Radio Resource Control (RRC) message, and the user terminal 100analyzes the information by the radio resource control unit 160.

The available MAC PDU size can be a set of MAC PDU sizes or a range ofMAC PDU sizes that the base station 200 can inform with thesemi-persistent transmission resource allocation message. The availableMAC PDU size can be expressed as a set of sizes, e.g. [size 1, size 2, .. . , size n], or as a range defined by minimum size and maximum size,e.g. [min size, max size]. The user terminal 100 verifies the CRC resultaccording to the available MAC PDU size.

For example, if the semi-persistent transmission resource allocationmessage indicates a MAC PDU size different from the available MAC PDUsize, the user terminal regards this message as the misrecognizederroneous message and ignores the corresponding semi-persistenttransmission resource allocation message.

The maximum number of resource blocks denotes the maximum number ofresource blocks that ban be allocated to the user terminal 100 with thesemi-persistent transmission resource allocation message. The userterminal 100 can verify the CRC result using the maximum number ofresource blocks. For example, if a number of resource blocks which isgreater than the maximum number of resource block are allocated, theuser terminals regards this message as the misrecognized erroneousmessage and ignores the corresponding semi-persistent transmissionsresource allocation message.

Next, the base station 200 transmits the semi-persistent transmissionresource allocation message to the user terminal 100 at step S405. Here,the semi-persistent transmission resource allocation message istransmitted on the Physical Downlink Control Channel (PDCCH). Thesemi-persistent transmission resource allocation message is protected by16-bit CRC, and the PDCCH occupies maximum 3 OFDM symbols per 1 msecacross the entire system bandwidth.

Particularly, the base station 200 transmits the semi-persistenttransmission resource allocation message based on the available MAC PDUsize and the maximum number of resource blocks transmitted at step S401.That is, the size of the resource to be allocated by means of thesemi-persistent transmission resource allocation message has not to beout of the available MAC PDU size and the maximum number of the resourceblocks.

Various formats of control message can be transmitted over PDCCH, andthe user terminal 100 attempts decoding on all the types and formats ofthe control messages.

An exemplary format of the semi-persistent transmission resourceallocation message is depicted in FIG. 5. The semi-persistenttransmission resource allocation message includes an RB assignment field(505), a Modulation and Coding (MCS) field (510), a Tx Power Control(TPC) field (515), and a Cyclic Redundancy Checking (CRC) field. Here,reference number 520 denotes other fields, and detailed descriptionthereon is omitted to avoid obscuring the subject matter of the presentinvention.

The RB assignment field 505 contains the information on the amount andlocation of the transmission resource to be used by the user terminal100. The transmission resource is allocated in unit of Resource Block(RB) which is 1 msec long across a predetermined bandwidth, and at leastone resource block is allocated by means of the RB assignment field 505.The MCS field 510 indicates the modulation schemed and channel codingrate for data transmission. The MCS field 510 is 5-bit long. The codepoint of the 5 bits is a combination of the modulation scheme andchannel coding rate. For example, the MCS field 510 can carry theinformation indicating any of 32 code points for the combinations from aQPSK modulation and 0.11 channel coding rate pair to 64QAM modulationand 0.95 channel coding rate pair. The TPC field 515 is a field forcontrolling the transmission power to be applied for the datatransmission. Although there can be other fields in addition to theabove described fields, detailed descriptions thereon are omittedherein. The CRC field 525 contains the information carried by thesemi-persistent transmission resource allocation message and the CRCresult to the C-RNTI for the semi-persistent transmission resourceallocation.

As described above, if the semi-persistent transmission resourceallocation message is received, the user terminal 100 determines whetherthe message is the semi-persistent transmission resource allocationmessage at step S407. The base station 200 can transmit the normaltransmission resource allocation message and the semi-persistenttransmission resource allocation message, and the base station 200 andthe user terminal 100 use different identifiers (C-RNTI) to distinguishbetween the normal transmission resource allocation message and thesemi-persistent transmission resource allocation message. The basestation 200 performs masking on the semi-persistent transmissionresource allocation message with the C-RNTI for semi-persistenttransmission resource allocation message. Next, the base station 200performs CRC operations and transmits the semi-persistent transmissionresource allocation message containing the CRC result. In order toidentify the semi-persistent transmission resource allocation message,the user terminal 100 performs masking on the received message with theC-RNTI for semi-persistent transmission resource allocation message.Next, the user terminal 100 performs CRC operation. If the CRC resultsare identical with each other, the user terminal 100 determines that thecorresponding message is the semi-persistent transmission resourceallocation message. Although the number of CRC operations attempted per1 msec for verifying the semi-persistent transmission resourceallocation message varies depending on the number of OFDM symbols forPDCCH transmission, it is about 20 times. For example, assuming that theCRC is 16-bit long, the false positive case can occur once among 65536operations. The message passed the CRC test can be a misrecognizederroneous message. This means that there can be and error inverification of the semi-persistent transmission resource allocationmessage.

Accordingly, even when a message is judged as the semi-persistenttransmission resource allocation message, there is a need for the userterminal 100 to verify the judgment result at step S409, i.e. whetherthe message is misrecognized erroneous message or not.

If it is determined that the message is not the misrecognized erroneousmessage, the user terminal 100 decides the semi-persistent transmissionresource allocated with the semi-persistent transmission resourceallocation message received at step S411.

Next, the user terminal 100 transmits the MAC PDUs in size indicated bythe semi-persistent transmission resource allocation message at stepS413. Since the user terminal 100 has to transmit the MAC PDUs to thebase station 200 without exchange of separate control signals, thesemi-persistent transmission resource allocation message decision mustbe accurate.

A description is made of a CRC operation result verification method ofthe user terminal hereinafter. The semi-persistent transmission resourceis most useful for the Voice over IP (VoIP) service, and the MAC PDU forthe VoIP service is limited in size. The present invention is conceivedin this point. According to an embodiment of the present invention, thebase station and the user terminal 100 limit the size of the MAC PDUavailable for transmission on the semi-persistent transmission resourceto reduce the occurrence of misrecognized erroneous message andminimize, if occurs, the damage caused by the occurrence of themisrecognized erroneous message.

Typically, there is a slight tendency in which the VoIP packets having acompressed header are regular in size. This is explained with referenceto FIG. 6. FIG. 6 is a drawing of graphs illustrating packet generationfrequency in accordance with code type and codec rate according to anembodiment of the present invention.

As shown in graph (a) of FIG. 6, assuming that the minimum packet sizeis x bytes at a codec rate A; x-byte packets occur most frequently,packets which is a few bytes longer than x bytes occur less frequently,and packets which is much longer than x bytes occur least frequently. Asshown in graph (b) of FIG. 6, assuming that the minimum packet size is ybytes at a codec rate B; y-byte packets occur most frequently, packetswhich is a few bytes longer than y bytes occur less frequently, andpackets which is much longer than y bytes occur least frequently. If itis possible to know the type and rate of the codec to be used in theVoIP service in consideration of such traffic characteristics, the userterminal can anticipate the size of the MAC PDU carrying the VoIPpackets.

In the wireless communication system according to an embodiment of thepresent invention, the size of MAC PDU to be carried on thesemi-persistent transmission resource is limited in the call setupprocess, e.g. VoIP bearer setup process. Table 1 shows the sizes of MACPDU that correspond to the codec rates according to an embodiment of thepresent invention.

TABLE 1 Codec rate Typical MAC PDU size 4.75 kbps 16 byte, 17 byte, 20byte 5.15 kbps 17 byte, 18 byte, 21 byte 5.90 kbps 19 byte, 20 byte, 23byte 6.70 kbps 21 byte, 22 byte, 25 byte 7.40 kbps 23 byte, 24 byte, 27byte 7.95 kbps 24 byte, 25 byte, 28 byte 10.2 kbps 30 byte, 31 byte, 34byte 12.2 kbps 35 byte, 36 byte, 39 byte

The frequently occurring MAC PDU sizes per codec rate with NB-AMR codecare shown in table 1. Accordingly, when setting up the bearer for theVoIP with NB-AMR codec, the sizes of MAC PDUs to be transmitted on thesemi-persistent transmission resource is limited to the sizes as shownin table 1.

That is, the base station 200 determines the available MAC PDU sizebased on the MAC PDU size occurring per type and rate of codec as shownin table 1 and notifies the user terminal with the available MAC PDU.Accordingly, when the MAC PDU size indicated in the semi-persistenttransmission resource allocation message is not any of the available MACPDU sizes, the user terminal 100 discards the corresponding message.That is, the CRC result is verified. Also, the CRC result verificationcan be performed by restricting the number of RBs as using the MAC PDUsize. According to an embodiment of the present invention, it ispossible to reduce the probability of occurrence of the misrecognizederroneous message through the verification process.

As described at step S401, in order to restrict the size of MAC PDU andthe number of resource blocks, the base station 200 notifies the userterminal 100 of the available MAC PDU sizes and the maximum number ofresource blocks.

In order to verify the CRC operation result, the user terminal 100compares the available MAC PDU sizes and maximum number of resourceblocks with the extracted MAC PDU size and number of resource blocks,respectively.

The user terminal 100 refers to the semi-persistent transmissionresource allocation message and calculates the size of MAC PDU to betransmitted on the semi-persistent transmission resource using equation(1):MAC PDU size=n*z*Y*number of bits per resource block.

In equation (1), n denotes a number of resource blocks, z denotes amodulation scheme, and y denotes a channel coding rate. Referring to thesemi-persistent transmission resource allocation message, n can beobtained by referencing the RB assignment field 505, and the z and y canbe obtained by referencing the MCS field 510. The variable z is 2 inQPSK, 4 in 16QAM, and 6 in 64 QAM. A number of bits that can betransmitted in a single resource block is preset.

Although the size of MAC PDU corresponding to the number of allocatedresource blocks and MCS information can be obtained using apredetermined equation, a value negotiated between the user terminal 100and the base station 200 can be used according to another embodiment ofthe present invention.

Although there are a few thousand combinations of the number allocatedtransmission resource and MCS information, large number of combinationsindicate the same MAC PUD size, and thus the indicative number of MACPDU sizes is about 180. For example, the MAC PDU sizes that arefrequently occurring in the NB-AMR as exemplary shown in table 1 is inthe range of 16 to 39 bytes and, since the sizes among the entire MACPDU sizes that are in that range is about 10, if restricting the rangeof the MAC PDU size between 16 bytes and 39 bytes, it is possible toreduce the occurrence probability of the misrecognized erroneoussemi-persistent transmission resource allocation message to 1/18.

Also, the number of resource blocks can be obtained from thesemi-persistent transmission resource allocation message. FIG. 7 is aflowchart illustrating a resource allocation method according to thefirst embodiment of the present invention.

Referring to FIG. 7, the user terminal 100 acquires the information onthe amount of the semi-persistent transmission resource through a callsetup process at step S701. Here, the information on the amount ofsemi-persistent transmission resource includes the available MAC PDUsizes and the maximum number of resource blocks. The information on theavailable MAC PDU sizes and the maximum number of resource blocks aretransmitted in the call setup process between the base station 200 andthe user terminal 100. That is, the user terminal 100 receives andstores the information on the available MAC PDU sizes and the maximumnumber of resource blocks in the call setup process. Here, the availableMAC PDU sizes can be expressed in the form of a set or a rage of MAC PDUsizes. The MAC PDU sizes are expressed as a set of individual MAC PDUsizes, e.g. [size 1, size 2, . . . , size n] or as a range with aminimum size and a maximum size, e.g. [min size, max size].

The user terminal 100 verifies the CRC result according to the availableMAC PDU sizes. In an exemplary case where the MAC PDU size indicated bythe semi-persistent transmission resource allocation message differsfrom the available MAC PDU sizes, the user terminal regards this messageas the misrecognized erroneous message and ignores the correspondingsemi-persistent transmission resource allocation message.

The maximum number of resource blocks is the maximum number of resourceblocks that can be allocated to the user terminal 100 with thesemi-persistent transmission resource allocation message. If the numberof resource blocks allocated by the semi-persistent transmissionresource allocation message is greater than the maximum number ofresource blocks, the user terminal 100 regards the message as themisrecognized erroneous message and ignores the semi-persistenttransmission resource allocation message.

The base station 200 transmits the information on the available MAC PDUsizes and the maximum number of resource blocks to the user terminal 100by means of the RRC message, and the user terminal 100 acquires theinformation by means of the wireless resource control unit 160.

After completing the call setup process, the user terminal 100 receivesthe message on the PDCCH at step S703 and performs decoding on thereceived message according a predetermined method at step S705.

The user terminal 100 performs masking on the decoded message with theC-RNTI for semi-persistent transmission resource allocation message atstep S707 and performs CRC operation on the message masked with theC-RNTI at step S709. Next, the user terminal 100 determines whetherthere is an error in the CRC operation result at step S711. If it isdetermined that there is an error in the CRC operation result, the userterminal 100 regards that the message is not destined to itself anddiscards the message with ignorance of its content. If it is determinedthat there is no error in the CRC operation result, the procedure goesto step S713.

At step S713, the user terminal 100 determines whether the number ofresource blocks indicated by the message is greater than the maximumnumber of resource blocks (checked previously at step S701) to verifythe CRC operation result at step S713. If the number of resource blocksis greater than the maximum number of resource blocks, this means thatthe message is the misrecognized erroneous message, and thus the userterminal 100 discards the corresponding message with ignorance of theits content at step S721.

If the number of resource blocks is not greater than the maximum numberof resource blocks, the user terminal 100 checks the MAC PDU size atstep S715. The MAC PDU size can be calculated using the transmissionresource allocation information and MCS information contained in thereceived semi-persistent transmission resource allocation message.

Next, the user terminal 100 determines whether the checked MAC PDU sizeis one of the available MAC PDU sizes at step S717. If the checked MACPDU size is not one of the available MAC PDU sizes, the user terminal100 determines that the misrecognized erroneous message is received, andthus discards the corresponding message with ignorance of its content atstep S721.

Otherwise, if the checked MAC PDU size is one of the available MAC PDUsizes, the user terminal 100 determines that the correct semi-persistenttransmission resource allocation message is received, and thus decidesthe semi-persistent transmission resource indicated by thesemi-persistent transmission resource allocation message at step S719and transmits the uplink data on the semi-persistent transmissionresource arriving periodically.

As described above, the CRC result verification process is performedaccording to an exemplary embodiment of the present invention. In theabove described embodiment, the verification is performed with twoparameters including available MAC PDU sizes and the maximum number ofresource blocks. However, the verification can be performed with one ofthe parameters. That is, one of the resource block-based verificationstep (S713) and the MAC PDU size-based verification steps (S715 andS717) can be omitted. Also, it is possible to perform the available MACPDU sizes-based verification step followed by the maximum number ofresource blocks-based verification step. That is, steps S715 and S717can be followed by step S713.

A description is made of the transmission resource allocation methodaccording to the second embodiment of the present invention. The normalsemi-persistent transmission resource includes the resource forretransmission. Accordingly, the transmission resource forretransmission is not allocated separately. According to the secondembodiment of the present invention, however, the user terminal isallocated a separate transmission resource to retransmit the firstpacket transmitted on the semi-persistent transmission resourceindicated by the semi-persistent transmission resource allocationmessage. Accordingly, in case that the semi-persistent transmissionresource allocation message received from the base station 200 is notdestined to the user terminal 100 itself, the user terminal 100 cannotbe allocated the transmission resource for retransmission. If noresource for retransmission is allocated, the user terminal 100determines regards the correctly received semi-persistent transmissionresource allocation message as a misrecognized erroneous message.

The aforementioned packet retransmission can be performed with anAutomatic Retransmission Request (ARQ) and/or Hybrid-ARQ (HARQ). In moredetail, after transmitting the semi-persistent transmission resourceallocation message, the base station 200 can transmit a separatetransmission resource allocation message for the HARQ retransmission ofthe first packet (unlike other HARQ retransmission or initialtransmission).

Meanwhile, if it is required to retransmit the first packet aftertransmitting the first packet on the semi-persistent transmissionresource indicated by the semi-persistent transmission resourceallocation message, and if a retransmission resource allocation messageis received from the base station 100, the user terminal 100 determinesthat the semi-persistent transmission resource allocation message is thecorrect one but not the misrecognized erroneous message so as to use theallocated semi-persistent transmission resource continuously.

This retransmission method entails a response to the retransmission.That is, if the HARQ retransmission is valid, the base station 100transmits an acknowledgement (ACK). If the ACK is received, the userterminal 200 determines that the corresponding semi-persistenttransmission resource allocation message is valid.

A description is made of the method according to the second embodimentof the present invention with reference to accompanying drawings. FIG. 8is a diagram illustrating a transmission resource allocation methodaccording to the second embodiment of the present invention. FIG. 8shows a structure of a frame used as transmission resource. In FIG. 8,the frame is divided into a plurality of subframes, and each subframe isdivided into a plurality of Resource Blocks (RBs). Here, it is assumedthat the semi-persistent transmission resource occurs at every 20subframes and HARQ Round Trip Time (RTT) is eight subframes.

Referring to FIG. 8, if the semi-persistent transmission resourceallocation message is received at a time point, the user terminal 100checks the transmission resource indicated by the semi-persistenttransmission resource allocation message. Next, the user terminal 100performs first HARQ retransmission of the first packet using theallocated transmission resource. Next, the user terminal 100 determineswhether a retransmission resource allocation message is received in asubframe which is allowed for transmitting an HARQ retransmissionresource allocation message. The HARQ retransmission resource isallocated by means of the normal transmission resource allocationmessage with the field containing a value indicating the retransmissionresource allocation. The subframes allowed for transmitting theretransmission resource allocation message are the subframes (915 to930) arranged at an interval of integer multiple of the HARQ RTT at thetime point 905 when the initial transmission resource allocation messageis received. Although the semi-persistent transmission resource isallocated, the user terminal does not judge that the semi-persistenttransmission resource allocation message is correct and use thesemi-persistent transmission resource indicated by the semi-persistenttransmission resource allocation message until the following twoconditions are fulfilled. That is, if an HARQ ACK to the transmission ofthe first packet on the semi-persistent transmission resource isreceived, or if a retransmission resource allocation message to thetransmission of the first packet is not received, the user terminal 100judges that the semi-persistent transmission resource is not verified.

If a valid retransmission resource allocation message is received in thesubframe 935, the user terminal confirms the allocation of thesemi-persistent transmission resource at that time and starts using theallocated semi-persistent transmission resource.

If it is determines that the semi-persistent transmission resourceallocation message received in the subframe 905 is the misrecognizederroneous message, the base station does not transmit HARQ ACK orretransmission resource allocation message to the user terminal 100.Since the user terminal 100 does not use the semi-persistenttransmission resource but for the first HARQ retransmission of the firstpacket, it is possible to minimize transmission resource waste caused bythe misrecognized erroneous message.

FIG. 9 is a flowchart illustrating a transmission resource allocationmethod according to the second embodiment of the present invention.Referring to FIG. 8, the user terminal 100 receives a message on thePDCCH at step S1001 and decodes the message at step S1003. Next, theuser terminal 100 performs masking the decoded message with a C-RNTI forsemi-persistent transmission resource allocation message at step S1005and performs CRC operation on the message masked with the C-RNTI at stepS1007. Next, the user terminal 100 determines whether there is an errorin the CRC operation result at step S1009. If there is an error in theCRC operation result, the user terminal 100 determines that the messageis not destined to itself so as to discard the message with ignorance ofits content. Otherwise, if there is no error in the CRC operationresult, the procedure goes to step S1010. At step S1010, the userterminal 100 attempts first HARQ transmission of the first packet usingthe transmission resource after x Transmission Time Interval (TTI).Next, the user terminal 100 determines whether an HARQ ACK to the HARQtransmission at step S1015 and, if the HARQ ACK is received, theprocedure goes to step S1020 and, otherwise, step S1025. If the HARQ ACKto the data transmitted on the allocated transmission resource, thismeans that the base station has received the uplink data successfullyand the transmission resource used for the data transmission is valid,such that the user terminal 100 decides the semi-persistent transmissionresource allocated with the received semi-persistent transmissionresource allocation message and transmits uplink data on thesemi-persistent transmission resource arriving periodically.

At step S1025, the user terminal 100 waits for the next ‘retransmissionresource allocation message-allowed subframe’. As aforementioned, the‘retransmission resource allocation message-allowed subframes’ are thesubframes (915, 920, 925, and 930) transmitted at an interval of integermultiple of HARQ RTT from the time point when the semi-persistenttransmission resource allocation message is received. In FIG. 8, theinterval is 8 subframes.

Next, the user terminal 100 determines whether the retransmissionresource allocation message is received in the subframes (915, 920, 925,and 930) at step S1030. If the retransmission resource allocationmessage is received, the user terminal 100 decides the semi-persistentresource at step S1020. For example, if a retransmission resourceallocation message is received in one of the retransmission resourceallocation message-allowed subframes (915, 920, 925, and 930), the userterminal 100 decides the semi-persistent transmission resource indicatedby the semi-persistent transmission resource allocation message. Inexemplary case of FIG. 8, the retransmission resource allocation message935 is received in the subframe 920.

If the retransmission resource allocation message is not received atstep S1030, the user terminal 100 does not use the allocatedsemi-persistent transmission resource, and the procedure goes to stepS1035.

At step S1035, the user terminal 100 determines whether a predeterminednumber of ‘retransmission resource allocation message-allowed subframes’has elapsed. If a predetermined number of ‘retransmission resourceallocation message-allowed subframes’ has elapsed, the procedure goes tostep S1040 and, otherwise, step S1025. At step S1040, the user terminal100 determines that the semi-persistent transmission resource allocationmessage is the misrecognized erroneous message and discards thesemi-persistent transmission resource allocation message with ignoranceof its content.

INDUSTRIAL APPLICABILITY

Although exemplary embodiments of the present invention have beendescribed in detail hereinabove, it should be clearly understood thatmany variations and/or modifications of the basic inventive conceptsherein taught which may appear to those skilled in the present art willstill fall within the spirit and scope of the present invention, asdefined in the appended claims.

The invention claimed is:
 1. A resource allocation method of a userterminal, comprising: performing Cyclic Redundancy Checking (CRC)operation on a semi-persistent transmission resource allocation messagereceived; verifying, when the CRC operation succeeds, validity of thesemi-persistent transmission resource allocation message by comparingtransmission resource information contained in the semi-persistenttransmission resource allocation message with a previously receivedradio transmission resource information; and using, when the validity ofthe semi-persistent transmission resource allocation message isverified, the transmission resource indicated by the semi-persistenttransmission resource allocation message semi-persistently.
 2. Theresource allocation method of claim 1, wherein verifying validity of thesemi-persistent transmission resource allocation message comprisesdetermining whether a MAC PDU size indicated in the semi-persistenttransmission resource allocation message is equal to one of MAC PDUsizes contained in the previously received radio transmission resourceinformation.
 3. The resource allocation method of claim 2, wherein theindicated MAC PDU size is a value obtained from a number of resourceblocks, a modulation scheme, a channel coding rate, and a number of bitsper resource block that are acquired from the semi-persistenttransmission resource allocation message.
 4. The resource allocationmethod of claim 1, wherein verifying validity of the semi-persistenttransmission resource allocation message comprises determining whether anumber of resource blocks indicated by the semi-persistent transmissionresource allocation message is less than a maximum number of resourceblocks of the previously received radio transmission resourceinformation.
 5. The resource allocation method of claim 1, furthercomprising discarding, when the CRC operation fails, the semi-persistenttransmission resource allocation message.
 6. The resource allocationmethod of claim 1, wherein verifying validity of the semi-persistenttransmission resource allocation message comprises: transmitting an HARQmessage to a first packet transmitted on the transmission resourceindicated by the semi-persistent transmission resource allocationmessage; and receiving at least one of an HARQ ACK in response to theHARQ message to the first packet and a retransmission resourceallocation message in response to the HARQ message.
 7. The resourceallocation method of claim 6, further comprising using, when at leastone of an HARQ ACK in response to the HARQ message and retransmissionresource allocation message in response to the HARQ message is received,the transmission resource indicated by the semi-persistent transmissionresource allocation message.
 8. The resource allocation method of claim6, further comprising discarding, when none of an HARQ ACK in responseto the HARQ message and retransmission resource allocation message inresponse to the HARQ message is received, the semi-persistenttransmission resource allocation message.
 9. A user terminal which isallocated transmission resource by means of a semi-persistenttransmission resource allocation message, comprising a reception unitwhich receives the semi-persistent transmission resource allocationmessage, compares, when no error is in CRC operation result,transmission resource information contained in the semi-persistenttransmission resource allocation message with a previously receivedradio transmission resource information to verify validity of thesemi-persistent transmission resource allocation message, and uses, whenthe validity of the semi-persistent transmission resource allocationmessage is verified, the transmission resource indicated by thesemi-persistent transmission resource allocation messagesemi-persistently.
 10. The user terminal of claim 9, wherein thereception unit verifies the validity of the semi-persistent transmissionresource allocation message by comparing a MAC PDU size indicated in thesemi-persistent transmission resource allocation message with MAC PDUsizes contained in the previously received radio transmission resourceinformation.
 11. The user terminal of claim 10, wherein the receptionunit calculates the MAC PDU size based on at least one of a number ofresource blocks, a modulation scheme, a channel coding rate, and anumber of bits per resource block that are acquired from thesemi-persistent transmission resource allocation message
 12. The userterminal of claim 9, wherein the reception unit verifies the CRCoperation result depending on whether a number of resource blocksindicated by the semi-persistent transmission resource allocationmessage is less than a maximum number of resource blocks of thepreviously received radio transmission resource information.
 13. Theuser terminal of claim 9, wherein the reception unit discards, if anerror is in CRC operation result, the semi-persistent transmissionresource allocation message.
 14. The user terminal of claim 9, furthercomprising a radio resource control unit which receives the radiotransmission resource information including at least one of availableMAC PDU sizes and maximum number of resource blocks from a base station.15. The user terminal of claim 9, wherein the reception unit verifiesthe validity of the semi-persistent transmission resource allocationmessage, after transmitting an HARQ message to a first packettransmitted on the transmission resource indicated by thesemi-persistent transmission resource allocation message, depending onwhether at least one of an HARQ ACK in response to the HARQ message tothe first packet and a retransmission resource allocation message inresponse to the HARQ message.
 16. The user terminal of claim 15, whereinthe reception unit uses, when at least one of an HARQ ACK in response tothe HARQ message and retransmission resource allocation message inresponse to the HARQ message is received, the transmission resourceindicated by the semi-persistent transmission resource allocationmessage.
 17. The user terminal of claim 15, wherein the reception unitdiscards, when none of an HARQ ACK in response to the HARQ message andretransmission resource allocation message in response to the HARQmessage is received, the semi-persistent transmission resourceallocation message.